package com.lk.study.encrypt;

import java.security.MessageDigest;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.spec.SecretKeySpec;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

public class AESEncryptUtil {
	
	public static String key = "";
	
	/**
	 * 结合base64实现md5加密
	 * @param msg 待加密字符串
	 * @return 获取md5后转为base64
	 * @throws Exception
	 */
	private static String md5Encrypt(String msg) throws Exception{
		return AESEncryptUtil.isEmpty(msg) ? null : base64Encode(md5(msg));
	}
	
	/**
	 * base 64 encode
	 * @param bytes 待编码的byte[]
	 * @return 编码后的base 64 code
	 */
	private static String base64Encode(byte[] bytes){
		return new BASE64Encoder().encode(bytes);
	}

	/**
	 * 获取字符串md5值
	 * @param msg 
	 * @return md5
	 * @throws Exception
	 */
	private static byte[] md5(String msg) throws Exception {
		return AESEncryptUtil.isEmpty(msg) ? null : md5(msg.getBytes());
	}

	/**
	 * 获取byte[]的md5值
	 * @param bytes byte[]
	 * @return md5
	 * @throws Exception
	 */
	private static byte[] md5(byte[] bytes) throws Exception {
		MessageDigest md = MessageDigest.getInstance("MD5");
		md.update(bytes);
		
		return md.digest();
	}

	private static boolean isEmpty(String msg) {
		return (null == msg || "".equals(msg)) ? true : false;
	}
	
	/**
	 * AES加密为base 64 code
	 * @param content 待加密的内容
	 * @param encryptKey 加密密钥
	 * @return 加密后的base 64 code
	 * @throws Exception
	 */
	private static String aesEncrypt(String content, String encryptKey) throws Exception {
		return base64Encode(aesEncryptToBytes(content, encryptKey));
	}
	
	/**
	 * 将密钥封装起来
	 * @param content
	 * @return
	 * @throws Exception
	 */
	public static String aesEncrypt(String content) throws Exception {
		return aesEncrypt(content, key);
	}

	/**
	 * AES加密
	 * @param content 待加密的内容
	 * @param encryptKey 加密密钥
	 * @return 加密后的byte[]
	 * @throws Exception
	 */
	private static byte[] aesEncryptToBytes(String content, String encryptKey) throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		// 解决linux下不可用的问题
		SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG" );  
        secureRandom.setSeed(encryptKey.getBytes()); 
		
		kgen.init(128, secureRandom);

		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(kgen.generateKey().getEncoded(), "AES"));
		
		return cipher.doFinal(content.getBytes("utf-8"));
	}
	
	/**
	 * AES解密
	 * @param encryptBytes 待解密的byte[]
	 * @param decryptKey 解密密钥
	 * @return 解密后的String
	 * @throws Exception
	 */
	private static String aesDecryptByBytes(byte[] encryptBytes, String decryptKey) throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		// 解决linux下不可用的问题
		SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG" );  
        secureRandom.setSeed(decryptKey.getBytes());
		
		kgen.init(128, secureRandom);
		
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(kgen.generateKey().getEncoded(), "AES"));
		byte[] decryptBytes = cipher.doFinal(encryptBytes);
		
		return new String(decryptBytes);
	}
	
	/**
	 * 将base 64 code AES解密
	 * @param encryptStr 待解密的base 64 code
	 * @param decryptKey 解密密钥
	 * @return 解密后的string
	 * @throws Exception
	 */
	private static String aesDecrypt(String encryptStr, String decryptKey) throws Exception {
		return AESEncryptUtil.isEmpty(encryptStr) ? null : aesDecryptByBytes(base64Decode(encryptStr), decryptKey);
	}
	
	/**
	 * 封装密钥
	 * @param encryptStr
	 * @return
	 * @throws Exception
	 */
	public static String aesDecrypt(String encryptStr) throws Exception {
		return aesDecrypt(encryptStr, key);
	}

	/**
	 * base 64 decode
	 * @param base64Code 待解码的base 64 code
	 * @return 解码后的byte[]
	 * @throws Exception
	 */
	private static byte[] base64Decode(String base64Code) throws Exception{
		return AESEncryptUtil.isEmpty(base64Code) ? null : new BASE64Decoder().decodeBuffer(base64Code);
	}
	
}
